Step 1 - Configure and verify that the Dialin and
Dialout clients are setup correctly. Since this configuration is focused on the
central site NAS configuration, we do not include a sample configuration for
clients. Some client sample configurations are included below:

Step 2 - Verify that the Telco circuits are
functioning properly. You can use the show isdn status command to verify that
the BRI or PRI circuit is functionting correctly. Refer to the document Using
the show isdn status Command for BRI Troubleshooting for more information. You
must also enable the T1/E1 PRI circuit for outbound calls. Contact your Telco
to verify this information.

Client: Cisco AS5300 with one T1 PRI circuit. This configuration is
not included.

Client: Cisco 1600 with one BRI circuit. This configuration is not
included.

Client: Cisco 804 with one BRI circuit. This configuration is not
included.

The information presented in this document was created from devices in
a specific lab environment. All of the devices used in this document started
with a cleared (default) configuration. If you are working in a live network,
ensure that you understand the potential impact of any command before using it.

In many situations, it may be necessary to use the same T1/E1 PRI
circuit for Dialin and Dialout connections. The Network Access Sever (NAS)
would support incoming calls from multiple ISDN users and it could also make
outbound calls on the same PRI to another device. The outbound dial could also
be used in a backup scenario, where the NAS would dial and connect to a peer
that loses its primary WAN link.

This configuration can be used with any router that has T1 or PRI
cards. Hence, any AS5xxx series router with a T1 or PRI card can use this
configuration. Cisco 2600 and 3600 series routers can also be configured to
accept ISDN calls with a T1/PRI WAN interface card (WIC) or Network Module.

This configuration can also be modified to be used with E1 or PRI
ports. Configure the E1 controller with the linecoding, framing and other
physical characteristics supplied by the Telco. The D-channel configuration
(interface Serial x:15 for E1s) is similar to the one shown here.

There are two primary methods for configuring an Access Server to be
able to make outgoing calls and accept incoming calls on the same T1/E1 PRI.
These are Dialer Profiles and Dialer Rotary Groups. Each has its benefits and
drawbacks, such as:

Dialer Rotary Groups are simpler to configure and
manage.

Dialer Profiles need a separate dialer interface for each incoming
and outgoing call.. If you have numerous incoming and outgoing peers then the
configuration will be complicated to create and maintain.

Dialer Profiles allow for client specific configuration. For example,
you can specify that a certain client will be assigned an IP address from
address pool A while another client will be assigned an address from pool B.

Dialer Rotary Groups allow only the same parameters to be applied to
all users. Per-user customization is not possible.

Dialer Rotary Groups only allow a single interesting traffic
definition for incoming and outgoing calls. Hence, you cannot configure the
router to use one interesting traffic definition for incoming calls and another
one for outgoing calls.

The above Dialer Profile configuration has a separate dialer interface
for each incoming and outgoing call. The dialer interfaces for the incoming
calls are Dialer 1 and Dialer 2, while the dialer interface for the outgoing
call is Dialer100. After the incoming call is authenticated, the router binds
the call to the appropriate dialer interface based on the dialer
remote-name. Only the dialer interface for the outgoing call
(Dialer100) has a dialer string with the number to be dialed. Only Dialer100
includes the dialer load-threshold command, since it can dial the additional
links depending on the inbound or outbound load (the default is outbound).

The following configuration uses Dialer Rotary Groups for this
scenario:

This section provides information you can use to confirm your
configuration is working properly.

Certain show commands are supported by the
Output Interpreter tool, which allows you to view an analysis of
show command output.

show isdn status - Ensures that the router
is properly communicating with the ISDN switch. In the output, verify that
Layer 1 Status is ACTIVE, and that the
Layer 2 Status state =
MULTIPLE_FRAME_ESTABLISHED appears. This command also displays
the number of active calls.

show ppp multilink - Displays information
on multilink bundles that are active. This command should be used to verify the
multilink connection.

show dialer [interface type
number] - Displays general diagnostic information for
interfaces configured for DDR. If the dialer came up properly, the
Dialer state is data link layer up message
should appear. If physical layer up appears,
then the line protocol came up, but the Network Control Protocol (NCP) did not.
The source and destination addresses of the packet that initiated the dialing
are shown in the Dial reason line. This show command
also displays the timer's configuration and the time before the connection
times out.

show caller user username
detail - Shows parameters for the particular user such as the IP
address assigned, PPP and PPP bundle parameters, and so on. If your version of
Cisco IOS software does not support this command, use the show
user command.

show dialer map - Displays configured
dynamic and static dialer maps. This command can be used to see if a dynamic
dialer map was created. Without a dialer map, you cannot route packets.

Below are some show command outputs for successful calls. Pay attention
to the bolded sections and the comments provided in the outputs. Compare the
output that you obtain with the result shown below.

debug ppp negotiation - Displays
information on the PPP traffic and exchanges while negotiating Link Control
Protocol (LCP), Authentication, and Network Control Protocol (NCP). A
successful PPP negotiation will first open the LCP state, then Authenticate,
and finally negotiate NCP. Multilink Parameters such as Maximum Receive
Reconstructed Unit (MRRU) are established during LCP negotiation.

Below is the debug outputs for a successful outgoing call. Pay
attention to the bolded sections and the comments provided in the outputs.
Compare the output that you obtain with the result shown below.